add accumulate example

.gitignore

@@ -10,3 +10,4 @@ typetest
 unique_ptr
 list-initializers
 array-bounds
+accumulate

CMakeLists.txt

@@ -8,3 +8,4 @@ add_executable(auto_ptr auto_ptr.cpp)
 add_executable(unique_ptr unique_ptr.cpp)
 add_executable(list-initializers list-initializers.cpp)
 add_executable(array-bounds array-bounds.cpp)
+add_executable(accumulate accumulate.cpp)

accumulate.cpp

@@ -0,0 +1,45 @@
+// http://www.cplusplus.com/reference/numeric/accumulate/
+
+#include <cassert>
+#include <iostream>
+
+#include <functional>   // std::minus
+#include <numeric>      // std::accumulate
+
+int myfunction (int x, int y) { return x+2*y; }
+
+struct myclass {
+  int operator()(int x, int y) { return x+3*y; }
+} myobject;
+
+int main() {
+  int init = 100;
+  int numbers[] = {10,20,30};
+  int res;
+
+  std::cout << "using default accumulate: ";
+  res = std::accumulate(numbers, numbers+3, init);
+  std::cout << res;
+  assert(res == 100+10+20+30);
+  std::cout << '\n';
+
+  std::cout << "using functional's minus: ";
+  res = std::accumulate(numbers, numbers+3, init, std::minus<int>());
+  std::cout << res;
+  assert(res == 100-10-20-30);
+  std::cout << '\n';
+
+  std::cout << "using custom function: ";
+  res = std::accumulate(numbers, numbers+3, init, myfunction);
+  std::cout << res;
+  assert(res == 100+20+40+60);
+  std::cout << '\n';
+
+  std::cout << "using custom object: ";
+  res = std::accumulate(numbers, numbers+3, init, myobject);
+  std::cout << res;
+  assert(res == 100+30+60+90);
+  std::cout << '\n';
+
+  return 0;
+}